"If we would have found a large decrease in test scores, I can't say I would have been surprised," says Mark Johnson, study co-author and researcher at Montana State University.

But that's not what happened.

Here's what Johnson and his co-researcher Mary Beth Walker actually found in analyzing data on more than 8,000 4th- and 5th-grade students in Colorado: Standardized test scores in math increased by up to 12% and scores in reading by 6% among schools with four-day weeks.

Overall, 3% of Colorado students attend schools with 4-day weeks. All of the schools are in rural areas.

The findings left many scratching their heads, including Johnson and Walker.

Administrators in schools that switched said that ditching a full day saved money that could then be reinvested in the other four days. When Johnson and Walker ran the numbers, however, that correlation didn't exist, so the explanation probably wasn't sound.

Another interpretation, Johnson says, is that they witnessed a small "attendance effect."

Basically, kids in urban areas can easily leave school for a dentist appointment a few blocks away — it won't disrupt the school day too much. In rural areas, like the locations with 4-day weeks examined in the study, parents might have to take their kids out of school for larger chunks of time to drive them further away. That's more disruptive.

Having a free Friday, in other words, might give rural and suburban parents the breathing room to shuttle kids to appointments without taking them out of school.

"Other than that, other important mechanisms we would've liked to study are some interesting teacher effects," Johnson says, such as an increase in productivity from taking an extra day to rest and regroup.

There are some difficulties in rebranding Friday or Monday as part of the weekend.

For one, most parents work five days a week. Older students might be able to find extra-curricular activities or part-time jobs to fill the time, and young kids could hang out in daycare, but 9 and 10 year olds — like the kids in Johnson and Walker's study — have nowhere to go after school.

The schools involved in the latest study were also small. All grades, from kindergarteners to high school seniors, learned in the same building. Any changes to scheduling would burden only a select few.

Still, if a school is innovative enough to consider the idea that kids learn better with less school, it can probably to figure out how to make the idea a reality. The trick is making that first leap.